Conventional installation of a switch or an outlet requires the provision of whatever switch, outlet, or switch-outlet combination, is necessary for the particular outlet site desired. The assembly is then nailed on a stud in ordinary practice such that it extends forward of the stud approximately the distance which would be occupied by the wallboard.
The wires are then pulled through a hole, or knockout, inside the box. The stripped conductors are then partially connected, with provisions made for the subsequent switch or receptacle to be installed. The partially completed connections are then stuffed (at least 6 inches per conductor) back into the wiring box to await wallboard installation.
The wallboard craftsman brings the large sheets of material up against the studs to be covered. The location(s) of the cutout(s) for the switch or outlet box(es) are then measured, estimated, and marked. The wallboard holes are then cut at the approximate locations marked. Now the wallboard is ready to be nailed onto the studs so that the wiring box(es) are accessible through the openings.
After the wallboard installation is finished, the electrician now must return to complete the job. The wires are now pulled back out of the wiring box, connections are then made to the switch or outlet device, and the wires are again crammed back inside the box while the device is screwed on the box. The final step is the installation of the screwed-on face plate.